chapter 8 human physiology. copyright © the mcgraw-hill companies, inc. permission required for...
TRANSCRIPT
Chapter 8
Human Physiology
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CNS
Consists of: Brain Spinal cord
Receives input from sensory neurons.
Directs activity of motor neurons.
Association neurons maintain homeostasis.
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Embryonic Development
Groove appears in ectoderm to fuse to form neural tube: Neural tube: CNS
Forebrain: Telencephalon and diencephalon
Midbrain: unchanged Hindbrain :Metencephalon and
myelencephalon Part of ectoderm where fusion
occurs becomes neural crest. Neural crest: Ganglia of PNS
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Embryonic Development Cavities of brain (ventricles)
become filled with CSF. Cavity (central canal) of spinal cord
also filled with CSF. CNS composed of gray and white
matter. Gray matter found in the cortex and
within nuclei. White matter (myelin) consists of axon
tracts.
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Cerebrum
Telencephalon. Largest portion
of brain. Responsible for
higher brain functions.
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Cerebral Cortex
Frontal: Precentral gyri: Involved in motor
control. Body regions with
the greatest number of motor innervation are represented by largest areas of motor cortex.
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Parietal Lobe
Primary area responsible for perception of somatesthetic sensation.
Body regions with highest densities of receptors are represented by largest areas of sensory cortex.
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Cerebrum
Temporal: Interpretation of auditory centers that
receive sensory fibers from cochlea. Interpretation and association of
auditory and visual information. Occipital:
Primary area responsible for vision and coordination of eye movements.
Deep insula: Involved in memory.
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Electroencephalogram (EEG)
Measured synaptic potentials produced in cell bodies and dendrites.
Used clinically do diagnose epilepsy and brain death.
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EEG Patterns Alpha:
Person is awake, relaxed, with eyes closed.
Beta: Produced by visual stimuli and mental
activity. Evoked activity.
Theta: Common in newborn, not found in
healthy adult.
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EEG Patterns Delta:
Common during sleep and awake infant.
In awake adult indicate brain damage. Sleep:
REM (rapid eye movement): Dreams occur. Low-amplitude, high-frequency waves. Similar to beta waves.
Non-Rem (resting): High-amplitude, low-frequency waves.
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Basal Nuclei Also called basal ganglia. Contains:
Corpus striatum: Caudate nucleus Lentiform nucleus:
Putman and globus pallidus
Masses of gray matter composed of neuronal cell bodies.
Function: Control of skeletal muscles. Control of voluntary movements.
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Cerebral Lateralization Cerebral
Dominance. Specialization of
one hemisphere. Left hemisphere:
More adept in language and analytical abilities.
Right hemisphere: Limited verbal
ability. Most adept at
visuospatial tasks.
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Language Broca’s area:
Involves articulation of speech. In damage to Broca’s area, comprehension
of speech in unimpaired. Wernicke’s area:
Involves language comprehension. In damage to Wernicke’s area, language
comprehension is destroyed, but can still speak.
Angular gyrus: Center of integration of auditory, visual,
somatesthetic information.
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Emotion and Motivation Limbic system: Center for basic emotional drives. Closed circuit between limbic system,
thalamus and hypothalamus. Amygdala produces rage and aggression. Amygdala and hypothalamus produce fear. Hypothalamus contains feeding and satiety
centers. Hypothalamus and limbic system involved in
the regulation of sexual drive and behavior. Hypothalamus and frontal cortex function in
goal directed behavior.
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Memory Short-term:
Memory of recent events. Medial temporal lobe: consolidates
short term into long term memory. Hippocampus is critical component
of memory. Acquisition of new information,
facts and events requires both the medial temporal lobe and hippocampus.
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Memory Long-term:
Requires activation of genes, leading to protein synthesis.
Growth of dendritic spines. Formation of new synaptic connections.
Cerebral cortex stores factual information.
Prefrontal lobes involve retrieval of parts of memories from different areas of the brain to use as a whole.
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Diencephalon
Comprised of the: Thalamus Hypothalamus Pituitary gland
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Thalamus
Composes the majority of the diencephalon.
Forms most of the walls of the 3rd ventricle.
Acts as relay center for all sensory information (except olfactory) to the cerebrum
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Hypothalamus Contains neural centers for hunger,
thirst, and body temperature. Contributes to the regulation of
sleep, wakefulness, emotions and sexual performance.
Stimulates hormonal release from anterior pituitary.
Produces ADH and oxytocin. Coordinates sympathetic and
parasympathetic reflexes.
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Pituitary Gland
Posterior pituitary: Releases ADH and oxytocin.
Anterior pituitary: Regulates secretion of hormones
of other endocrine glands.
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Midbrain Contains:
Corpra quadrigemina Cerebral peduncles Substantia nigra Red nucleus
Functions: Visual reflexes. Relay center for auditory information. Motor coordination.
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Hindbrain
Metencephalon: Pons:
Contains the apneustic and pneumotaxic respiratory centers.
Cerebellum: Receives input from proprioceptors. Participates in coordination of
movement.
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Hindbrain
Myelencephalon (medulla): All descending and ascending fiber tracts
between spinal cord and brain must pass through the medulla.
Vasomotor center: Controls autonomic innervation of blood vessels.
Cardiac control center: Regulates autonomic nerve control of heart.
Regulates respiration with the pons.
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Ascending Spinal Tracts
Convey sensory information from cutaneous receptors, proprioceptors and visceral receptors to cerebral cortex.
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Descending Spinal Tracts
Pyramidal tracts descend directly without synaptic interruption from cerebral cortex to spinal cord. Fine movements.
Reticulospinal tracts (extrapyramidal): Gross motor
movement.
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Reflex Arc
Stimulation of sensory receptors evokes AP that are conducted into spinal cord.
Synapses with motor neuron.
Conducts impulses to muscle and stimulates a reflex contraction.
Brain is not directly involved.